JPH0222505A - Laser interference measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure the shape of a fine part by picking up an image of a measured surface with low magnification and high magnification under the same conditions. CONSTITUTION:The light beam emitted by a laser light source 10 is changed in direction by 90 deg. through a mirror 12 and the made into parallel luminous flux by a beam expander 14 to be made incident on a half-mirror 16. This light beam is changed in direction by 90 deg. and the light is emitted on the surface 18 to be measured and also emitted on a reference surface 20. The reflected light beams from the surface 18 to be measured and reference surface 20 are made incident on a low-magnification image forming lens 26 through a beam splitter 24. Further, the light beam which is reflected by the splitter 24 is made incident on a high-magnification image forming lens 30 as interference light. Further, a camera 28 for low-magnification measurement picks up an image of interference fringes corresponding to the low magnification and sends its image signal to a memory 34. Further, a camera 32 for the high magnification picks up an image of interference fringes corresponding to the high magnification and sends its image signal to a memory 40. Thus, the shape of the fine part is accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser interference measurement device, and more particularly to a laser interference measurement device equipped with an optical system for low magnification observation and an optical system for high magnification observation.

[Conventional technology]

Conventionally, while irradiating a measurement mirror and a reference mirror with laser light,
A laser interference measurement device is known that interferes with the reflected light and measures the surface shape (degree of surface irregularity) of the object to be measured from the intensity of interference fringes of the interference light.

Furthermore, among such laser interference measurement devices, a laser interference measurement device including a low-magnification observation optical system and a high-magnification observation optical system is also known. Laser interference measurement equipment equipped with such a low-magnification observation optical system and a high-magnification observation optical system is of the type that uses a zoom optical system to switch the magnification, and has multiple objective lenses, which can be exchanged using an interchangeable lens system. There are some that change the magnification. A laser interferometer with such a magnification switching mechanism first observes the surface to be measured using a low-magnification optical system, and then switches to a high-magnification optical system to measure the required minute part at high magnification. There is.

[Problem that the invention seeks to solve]

However, in the conventional laser interferometer with a magnification switching mechanism, time has elapsed between the time of observation with the low-magnification optical system and the time of observation with the high-magnification optical system, and the observations are not made under the same conditions. There is a possibility that it will not happen. For example, observation of such a laser interference measurement device is performed using an imaging camera, but when observed under magnification, the brightness and darkness of the interference fringes may be due to the surface shape of the measurement surface, the tilt of the workpiece over time, or the presence of air. Since it is impossible to determine whether the brightness or darkness of the interference fringes is due to the effects of fluctuations etc. as time has passed, the relative inclination and relative height of the surface shape measured at high magnification with respect to the surface shape measured at low magnification are measured. There are some problems such as not being able to do it. Such a phenomenon occurs particularly when measuring on the order of 1/100 μm, which is used to measure the surface shape of a magnetic head.

The present invention has been made in view of these circumstances, and it is an object of the present invention to propose a laser interference measurement device that can perform observation using a low-magnification optical system and a high-magnification optical system under the same conditions.

[Means for solving problems]

The present invention provides a laser interference measurement device that irradiates a measurement mirror and a reference mirror with a laser beam, causes the reflected light to interfere with each other, and measures the surface shape of a workpiece based on the intensity of interference fringes of this interference light. A beam splitter is provided to separate the interference light into two beams, and one of the separated lights is guided to a low-magnification imaging optical system including an imaging camera, and the other light is guided to a high-magnification imaging optical system including an imaging camera. The present invention is characterized in that it is provided with a memory means for storing an image signal from an imaging camera and a display means for displaying an image taken at a low magnification and an image taken at a high magnification.

[Effect]

In the laser interference measurement device according to the present invention, interference fringes can be observed simultaneously using both the low-magnification optical system and the high-magnification optical system. Therefore, first, an image is taken with a low magnification optical system and an image signal such as the surface shape is stored in a memory means, and at the same time an image is taken with a high magnification optical system and the image signal is recorded in a memory means. Both the shape imaged by the camera and the shape imaged by the high-magnification optical system are displayed on a CRT screen or a printer. As a result, it is possible to observe at both low magnification and high magnification under the same conditions.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the laser interference measurement apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the structure of a device for measuring a surface shape using a laser interference measuring device according to the present invention, in which lO is a laser light source, 12 is a mirror, 14 is a beam expander, and 16
is a half mirror. Further, 18 is a surface to be measured, 20 is a reference surface, 22 is a piezo element, 24 is a beam splitter,
26 is an imaging lens for low magnification, 28 is a camera for low magnification measurement, 30 is an imaging lens for high magnification, and 32 is a camera for high magnification measurement. The image signal captured by the camera 28 is stored in the memory 34
After being recorded in C and image processed by computer
It is designed to be displayed on the RT screen 38 or on a printer or the like. Furthermore, the image signal taken by the high-magnification measuring camera 32 is recorded in a memory 40, subjected to image processing by a combination camera 36, and then displayed on a CRT screen 38 or a printer.

In the laser interference measurement apparatus configured as described above, the light emitted from the laser light source 1O is converted into a parallel light beam by the beam expander 14 after being changed in direction by 90 degrees by the mirror 12, and then enters the half mirror 16. The direction of the light incident on the half mirror 16 is changed by 90°, and the light is emitted toward the measurement surface 18 and the reference surface 20 . The reflected light from the measurement surface 18 and the reference surface 20 passes through the beam splitter 24 and enters the low-magnification imaging lens 26 as interference light. On the other hand, the light reflected by the beam splitter 24 enters the high magnification imaging lens 30 as interference light. The low magnification measurement camera 28 captures an image of interference fringes at low magnification, and the image signal is sent to the memory 34 .

Furthermore, the high-magnification measurement camera 32 captures a high-magnification interference fringe image of a specific portion, and the image signal is sent to the memory 40 .

Therefore, for example, on the CRT screen 38, a three-dimensional figure P at a low magnification and a minute three-dimensional figure Q at a high magnification under the same conditions are displayed as shown in FIG. 2 using convenience store graphic technology. Become.

In FIG. 2, a three-dimensional figure is displayed based on interference fringes, but the present invention is not limited to this, and interference fringes may be directly displayed.

〔Effect of the invention〕

As explained above, according to the laser interference side device according to the present invention, it is possible to image the measurement surface under the same conditions at low magnification and high magnification, so it is possible to accurately measure the shape etc. of minute parts. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of a laser interference measurement device according to the present invention, and FIG. 2 is an explanatory diagram showing a three-dimensional view of a surface shape observed by the laser interference measurement device according to the invention. 10... Laser light source, 18... Surface to be measured, 20
...Reference plane, 28...Low magnification measurement camera,
32...High magnification measurement camera, 34.40...
Memory, 38...CRT screen. ! , Indication of the case 20 Title of the invention 3 Address of the person making the amendment Name 4 Name of the address of the agent Procedural amendment 1986 Patent application No. 172278 Laser interference measurement device

Claims (1)

[Claims] (1) In a laser interference measurement device that irradiates a surface to be measured and a reference mirror with a laser beam and causes the reflected light to interfere with each other, the surface shape of the object to be measured is measured from the intensity of interference fringes of this interference light. A beam splitter is provided to separate the interference light into two beams, and one of the separated lights is guided to a low-magnification imaging optical system including an imaging camera, and the other light is guided to a high-magnification imaging optical system including an imaging camera. 1. A laser interference measurement device comprising: a memory means for storing an image signal from an imaging camera; and a display means for displaying an image taken at a low magnification and an image taken at a high magnification.